1. Populate the MusicBrainz release and recording ID of a file
2. Save the file
3. Close Tag
4. Launch Tag
5. Open the file
6. Check the MB tags in the Misc tab and they are not populated.

I would assume they should be saved but I do not see that they are.

On a related note, if the Echo Nest ids are retrieved should it save those? I don't see them in the tabs. I'm not sure if there is a standard tag name for any of these fields but it seems incredibly useful to have that information since it identifies the release and track.

Using some command-line ID3 tools such as id3info and id3v2, I cannot determine if the tags are set.